Thermostatically controlled clutch



Oct. 1, 1963 R. J. sE'rTlMl- 1I'HERMos'm'rICALLY coNTRoLLED CLUTCH FiledDec. 31, 1959 United States Patent O 3,105,580 TIERMGSTATICALLYCONTROLLED CLUTCH Raymond I. Settimi, Letchworth, Herts, England,assigner to Borg-Warner Corporation, Chicago, Ill., a corporation ofillinois Filed Dec. 31, 1959, Ser. No. 863,136 17 Claims. (Cl. 1912-82)This invention relates to clutch devices and more particularly, toclutch devices responsive to lambient temperature conditions andparticularly suited for controlling the engagement between a drivingmeans and a driven device such, for example, as afan.

It is an object of the present invention to provide a clutch mechanismfor engaging and disengaging a fan device in response to enginetemperatures.

It is a further object to provide a simple and inexpensive clutch deviceof the friction iband type for engaging a fan `device with a drivingmeans at a predetermined temperature of the air surrounding such clutchdevice.

Another object is to provide an -improved thermally actuated clutchdevice wherein the thermal actuating device is a -bimetal element lfixedto the driven member and adapted to engage the fan assembly with thedriving member under certain temperature conditions and disengage thefan assembly from the driving member under other temperature conditions.

It is a further object of this invention to provide an improved clutchmechanism wherein the initial engagement between the driven and drivingmembers is accomplished by means of a thermal element urging a frictionband into initial engagement with the driving member, the clutch devicebeing so constructed that further engagement Will be effected bycentrifugal force and the inherent self-energizing characteristics ofthe friction band.

A still further object is to provide a clutch mechanism which willprovide a quick lock-up and quick release without excess slippage.

Other objects and features of the invention Ivvill be readily apparentto those skilled in the art from the specication and appended drawingsillustrating a preferred embodiment of the invention in which:

FIG. 1 is an elevational View in section;

FIG. 2 is an end sectional View taken along the line 2 2 of FIG. 1;

FIG. 3 is a partial right end view of the device shown in FIG. 1; and

FIG. 4 is a view in perspective of a multiple wrap friction band.

The device shown in FIG. 1 and constructed in accordance with theprinciples of this invention comprises generally, a driving member 1G, adriven member or fan carrier 12 having mounted thereon a fan assembly14, a clutching element in the nature of an annular friction band 16 anda thermal element 18 for actuating the friction band 16 to accomplish adriving engagement between the driven member 12 and the driving member10.

The driving member I()i which may be an aluminum casting, for example,has formed at its one end a generally annular flange 20 for connectionto a complementary annular plate 22 by suitable means such as aplurality of bolts 24. The annular plate 22 is xedly attached to a shaft26 of a water pump (not shown). The water pump shaft 26 and the waterpump attached thereto are adapted to be `driven in a conventional mannerby a fan belt 28 through a pulley 30, the pulley 3G being bolted to theannular plate 22. The driving member 16 has centrally formed therein anopening 32 to receive the end of the Water pump shaft 26. It will benoted that the annular plate 22, lthe pulley 30 and the flange35,165,580? Patented Oct. l, 1963 ICC 20 are bolted together by thebolts 24, the shaft 26 extending through central openings in the plate22 and the pulley 30 and into the opening 32 of the driving member. Thusthe driving member 10 is driven at all times and at the same speed asthe water pump shaft 26.

At its right end, as viewed in FIG. 1, there is for-med on the drivingmember 10 a hub or drum 34, the inner annular periphery 36 thereof beinglined with a drum liner 318. The inner periphery 4t) of the drum linerfunctions as a clutching surface. The inner periphery 36 of the drum 34and the outer periphery of the liner 38 may have complementaryserrations and projections formed thereon to prevent relativecircumferential movement between -the drum 34 and the liner 38. Alsoformed in the `driving member 10 is a central opening 42 for receiving adrive shaft 44. The drive shaft 44 may be press fitted, for example,into the central openin-g 42.

The ldriven member 12 of this ydevice serves as a fan carrier. Thedriven member comprises a spider 46 which may be made of cast aluminum,for example. The spider 46 is adapted to receive the fan assembly 14which may be bolted to the spider by means of a plurality of bolts 48.The spider 46 is journalled for free rotation around the drive shaft 44by means of a double row of bearings 50 `disposed between inner races 52and outer races 54.

The clutching element `16 comprises an expandable metal band '56 on theouter periphery lof which is attached a band of friction material 58.This clutching element may comprise a single Wrap band as illustrated inFIG. 2 or may lcomprise a multiple wrap band, ie., one which extendsmore than 360, as illustrated in FIG. 4. The friction material 5S may beattached to the metal band 56 by a conventional bonding process. Thefriction material 58 may be made, for example, from material identifiedas Gatke brake lining Style #2.460. On one end 0f the metal band 56there is formed a radially inturned portion 60. In an assembledcondition, the portion 60 is fitted into a radially extending slot 61formed in the spider 46. In an assembled condition (see FIG, 2), theslot 61 serves as an anchor point for the inturned portion 60 of thefriction band, the friction band being anchored in such a way that theportion 60 may move Ionly in a substantially radial `direction relativeto the spider. No substantial circumferential movement of the frictionband with respect to the spider is possible.

The other end 62 of the friction band 16 is loose and may be referred toas the trailing end 62. eAs viewed in FIG. 2, the driving member 10 willnormally rotate in a clockwise direction as indicated by the arrow. Itwill be noted that the wrap of the friction band 16 is in acounterclockwise direction progressing from the point at which theportion 60 is anchored in the slot 61 of the spider 46. Eixedly:attached to the trailing end 62 of the friction band 16 at the 'innerperiphery thereof is an axially extending control ta'b 63 having formedtherein an axilally extending slot 64. 'I'he control tab `63 may be spotWelded to the metal band 56.

'["ne thermal element 18 sometimes referred to as a thermostaticactuating device or temperature responsive means comprises a bimetalelement 65 made in the form of a spiral coil `as shown Iin FIG. 3. Thebimetal element 65 is secured to an annular member 66. The member 66,which may be made in the form of a stamping, comprises an axiallyextending hub portion 68 and a radially extending annular flange 70extending from the edge of said hub. A plurality of holes 72 are formedin the flange 7i) for securing the annular member to the spider 46. Thehub portion 68 is formed at the center of the annular member 66 andprojects axially as shown in FIG. l. Formed in the hub portion 68 is aslot 74 for receiving an inner radially inwardly extending tab 76 formedon the inner end of the bimetal element 65.

Formed on the outer end of the spiral bimetal element 65 is a radiallyoutwardly extending tab 78 lying in substantially the same plane as thetab 76.

The fan assembly 14 comprises a central ange portion 80 from which mayextend a plurality of blades 82. A oircumferentially extending slot S4extending through an arc of 'approximately 30o for adequate clearance isformed in the flange portion 89. In the assembled device the control tab63 of the friction band 56 extends through the slot 84 and is positionedwith relation to the bimetal element 65 so that the radially extendingtab 7S of the bimetal element `65 is received by the slot 64 of thecontrol tab 63. An aperture 86 is centrally formed in the ilange portionSil so that when assembled this aperture ts around the outermost portionof the bearing 50. Thus in an assembled condition, as shown in FIG. l,the spider `46 which is journatlled on the drive shaft 44, the angeportion 8i? of the fan assembly 14 and the radially extending annularflange 7G of the annular member 616 are all secured together by aplurality of bolts 48.

Operation Before describing the :operation of this device, it should bepointed out that one fof the purposes of this device is to providesimple mechanism which will permit a fan assembly to remain in Iadisengaged condition while ambient temperatures are below a certainpredetermined lgure. When the temperature of the surrounding air risesto a certain predetermined tigure, the fan is then to be engaged by thedriving member and continued in operation until the temperature of thesurrounding air -is again reduced to a certain temperature whendisengagement of the fan will again be effected.

It will be noted in the operation of this device, that the drivingmember .10, which is connected to the water pump shaft, as illustratedin LFIG, 1, will at all times be driven along with the water pump shaftby the pulley 30. During this rotation of Ithe driving member 10, thedriven member 12 will rotatingly oat on the drive shaft 44. There willin all probability be some rotation of the driven member 12 and the fanassembly 14 assembled thereon due to the riotional drag of the bearings50 which cannot be completely eliminated. It will be noted that whilethe driven member 12 is not engaged with the driving member 10, there isno power consumption by the driven member and this, of course, is one ofthe desirable results sought to be obtained.

A device of this type in an automotive environment would normally belocated immediately to the rear of the radiator of a vehicle, a radiatorbeing shown schematically in FIG. 1 at 8S. As is well known, in aconventional automobile a coolant circulating through an engine iscirculated through a radiator, -thus heating the radiator and the airwhich would normally pass through the radiator 4from the front -to ftherear and over the engine. Assuming that this device is loca-tedimmediately to the rear of an automobile radiator as shown in FIG. 1, itis apparent that the temperature surrounding this device will increasewith increase in engine temperature. It is desirable, if possi-ble,:that engine temperature be increased to a predetermined amount but thatit not exceed a certain upper range. `On the `other hand, it is alsodesirable to keep the engine temperature and the temperature of the airsurrounding an engine above a certain lower limit to help maintainmaximum eiciency. Thus it would ybe well to dispense with the coolingelects of a constantly rotating fan when the engine temperature andtemperature of air flowing over the engine reaches a relatively lowvalue and to have the tan engage to provide a ilow of cooling air whenthe engine temperature is at a relatively higher value. In operation,when the engine temperature increases to a certain predetermined value,4the coils of the bimetal element 65 will tend to expand in theparticular construction shown. The different coefficients of expansionof the bimetal element 65 i will cause the coils of the bimetal elementto expand and thus, to move the outer tab 78 in a clockwise direction asindicated by the arrow in FTG. 3. This clockwise movement of the tab 78moves the trailing end 62 of the friction band 16 circumferentially tothe right as seen in FIG. 2, thereby radially expanding the entireclutching element 16. As soon as ythe clutching element 16 is expandedsufficiently to make an initial contact with the clutching surface 4t)formed on the inner periphery of the drum liner 38, this initialfrictional engagement will cause rotational movement of the drivenmember 12. As this frictional engagement increases, the speedv of thedriven mem-ber increases being eiect-ive to exert a coustantlyincreasing centrifugal force on the clutching element 16. Eventually,the self-energizing characteristics of the clutching element 16 effect acomplete engagement lbetween the clutching element and the `clutchingsurface 4t) so that the driven member 12 and the fan assembly 14attached thereto assume the same speed as the driving member 10. It isto be noted here that the thermal element 18 is eiective only to causethe initial engagement `of the clutching element 16 with the clutchingsurface 4i). It is not contemplated that the force exerted by thethermal element 18 -will be sucient to expand the clutching element 16with suflicient force to effect in and of itself a complete and positiveengagement between the driving and driven members. I

As the rotating fan cools the air the coils of the thermal element willtend to contract and tend to move the outer tab 78 counter-clockwise,and a torque will be exerted on the trailing end 62 of the clutchingelement 16 `in a direction tending to ,free this trailing end fromengagement with the clutching surface. This torque builds upprogressively as the degree of cooling progresses until it is able toovercome 'both the centrifugal and engaging force inherent in the drivenclutching element. Due to the accumulated torque, when the `.disengagingaction once begins, it goes to complete engagement rather quickly. Sincethe centrifugal force becomes 'less and less as the fan becomespartially disengaged, it is apparent that this engagement once begun,progresses rapidly'.

Thus it can be seen that this device advantageously provides a simplyconstructed thermally actuated friction band clutching mechanism -forengaging and disengaging an automobile engine cooling fan in response tovarying temperature cond-i-tions. This device advantageously allows acooling fan to remain in a disengaged position at a relatively lowengine operating temperature when excess cooling would not be desirable,and it also provides for engagement of the fan when such cooling effectseventually are required.

It should also be pointed out that while the embodiment here describedhas been described in relation to an automotive environment, such aclutching device may lbe used in a variety of other instances whereselective engagement and disengagement `ot a driven device are desired.

While a certain preferred embodiment of the invention has beenspecifically disclosed, it is understood that the invention is notlimited thereto as many variations will be readily apparent to thoseskilled yin the art and the invention is to be given its broadestpossible interpretation within `the terms of the following claims.

I claim:

l. A clutch mechanism comprising: a driving member,

a driven member coaxially mounted on said driving member for oatingrotation thereon, an axially extending radially expansible one piecelband clutching element mounted on said driven member for drivinglyconnecting said driving and driven members, and thermally responsivemeans mounted on said driven memlber and connected -to said clutchingelement for urging said clutching lelement into position to drivinglyconnect said driving and driven members.

2. The device of claim l wherein said thermally responsive meanscomprises a bimetal element one end thereof being connected to saiddriven member and the outer end -being connected to said clutchingelement for displacing said clutching element relative to said drivenmember and for moving said -clutching element into engagement with saiddriving member -to thereby initiate a drive between said driving anddriven members.

3. The device of claim l wherein .said clutching element comprises aradially and circumferentially expandable friction band and wherein saidthermally responsive means comprises a bimetal element the inner endthereof 'being connected to said driven member and the outer end beingconnected `to said clutching element, said bimetal element being soconstructed and arranged that in response to an increase in thetemperature `of said bimetal, said clutching element will be urged to anengaging position.

4. A self-energizing band clutch comprising: a driving member, a drivenmember coaxially mounted on said driving member for floating rotationthereon, a one piece split friction band clutching element mounted onsaid driven member for drivingly connecting said driving and drivenmembers and means for bringing said clutching element into engagementwith said driving member, said means comprising a thermally actuatedelement.

5. The device of claim 4 wherein said thermally actuated element ismounted on said driven member.

6. A clutch mechanism comprising: a driving member having formed thereona drum, said drum being provided with means defining an internalclutching surface; a driven member coaxially and rotatably mounted onsaid driving member; a radially expandable clutching element mounted onsaid driven member for drivingly connecting said ldriving and drivenmembers; means connected to said driven member for radially expandingsaid clutching element, said means comprising a bimetal coil connectedat `one end to said -driven member and at the other end to saidclutching element, said bimetal coil being effective to radially expandsaid clutching element to initial engagement with said internalclutching surface in response to a predetermined change in temperature.

7. In a clutch device to effect engagement between a driving member anda ivehicle fan, the combination comprising a driving member adapted Itobe rotated, a driven member concentrically and rotatably mounted on saiddriving member, friction band means mounted on said driven member andconnected at one end thereof to said driven member, thermally actuatedmeans connected to the other end of said friction band means andcomprising a bimetal element operable to eifect radial expansion of saidfriction band means to establish a torque transmitting 'drive betweensaid driving and driven members through said friction band means.

8. The device of claim 7 wherein the bimetal element comprises a spiralcoil, said bimetal element being connected to said friction band meansto effect expansion and consequent engagement of the friction band meanswith the driving member when said bimetal element is subjected totemperatures in a predetermined range.

9. The device of claim 7 wherein the bimetal element comprises a spiralcoil, said bimetal element being connected to said friction band meansto eiect expansion and consequent engagement of the friction band meanswith the driving member at relatively higher .temperature conditions andfurther to effect contraction and consequent disengagement of thefriction band means with the driving member at relatively lowertemperature conditions.

10. The device of claim 7 wherein the bimetal element is operable toeffect circumferential movement of said friction band relative to saiddriven member and in the same 'direction as the direction of rotation`of said driving member to effect a self-energizing clutching action.

11. A clutch mechanism comprising: a driving member adapted to berotated and having a hub formed there'- on, an internal clutchingsurface formed on said hub, a driven member coaxially and rotatablymounted in relation to said hub, a clutching means comprising a singlewrap internal friction band mounted on and loosely connected to saiddriven member to permit radial displacement of said friction band, athermally responsive element comprising a bimetallic expansible spiralcoil, means connecting the inner end of said thermally responsiveelement to said driven member and means connecting the outer end of saidthermally responsive element 'to said friction band, said thermallyresponsive element when heated to a predetermined temperature beingeffective to move said friction band into engagement with said internalclutching surface.

l2. A clutch mechanism comprising: a driving member adapted to berotated, an internal clutching surface formed on said driving member, adriven member, a clutching element comprising a one piece split frictionband for establishing a driving connection between said driving anddriven members, said friction band having a rst end thereof connected toan anchor point on said driven member so as to permit radial movement ofsaid rst end and a trailing end which is free to be radially expanded,said friction band being wrapped from said anchor point within saiddriving member in a direction opposite to the normal rotation of saiddriving member, and an actuating device connected to said trailing endof said friction band, said device when actuated being eifective toexpand said trailing end into initial engagement with said internalclutching surface.

13. The clutch mechanism of claim l2 wherein the actuating devicecomprises a thermal element fixed to said driven member and connected tosaid trailing end of said friction band so that said thermal element inresponse to a predetermined amount :of heat will be effective to expandsai-d friction band into initial engagement with said clutching surface.

14. A cooling fan assembly comprising: a driving member including a drumportion having a clutching surface formed on the internal peripherythereof; a driven member rotatably mounted on said driving member forfloating rotation thereon; a fan mounted on said driven member to Ibedriven therewith; an axially extending radial expansible one-piece splitfriction band means rfor intermittently connecting said driving :anddriven members, said band having two ends; means connecting one end ofsaid friction band to the driven member; actuating means iixedlyattached to the driven member for intermittently connecting the drivingand driven members by expanding the Vfriction band means into engagementwith said Iclutching surface, said actuating means comprising athermally responsive means; and means connect-ing the actuating means tothe other end of said friction band means.

15. A cooling yfan assembly comprising: a driving member adapted to bedriven by a power source and including a drum portion having a clutchingsurface formed on the internal periphery thereof; a hub portion formedon said driving member; a driven member rotatably mounted on said hubportion of said driving member for floating rotation thereon; a fanmounted Ion said driven member to be driven therewith; an axiallyextending radial expansible one-piece split friction band means forintermittently connecting said driving and driven members, said bandhaving two ends; means connecting one end of said fliction band to thedriven member, said means being constructed and arranged to permit saidone end to move outwardly into engagement with said clutching surface;actuating means iixedly attached to the driven member for intermittentlyconnecting ythe driving and driven members by expanding the frictionband means into engagement with said clutching surface, said actuatingmeans comprising a thermally responsive means; and means conment, saidmeans extending through said fan assembly.

1. A CLUTCH MECHANISM COMPRISING: A DRIVING MEMBER, A DRIVEN MEMBERCOAXIALLY MOUNTED ON SAID DRIVING MEMBER FOR FLOATING ROTATION THEREON,AN AXIALLY EXTENDING RADIALLY EXPANSIBLE ONE PIECE BAND CLUTCHINGELEMENT MOUNTED ON SAID DRIVEN MEMBER FOR DRIVINGLY CONNECTING SAIDDRIVING AND DRIVEN MEMBERS, AND THERMALLY RESPONSIVE MEANS MOUNTED ONSAID DRIVEN MEMBER AND CONNECTED TO SAID CLUTCHING ELEMENT FOR URGINGSAID CLUTCHING ELEMENT INTO POSITION TO DRIVINGLY CONNECT SAID DRIVINGAND DRIVEN MEMBERS.